1. Field of the Invention
This invention relates to glass container manufacturing and more particularly to an improved plunger assembly useful in initial formation of the parison in the blank mold.
2. Description of the Prior Art
The most commonly employed machine for glass container manufacture is the individual section (I.S.) machine wherein the various individual operations involved in glass container manufacture are sequentially performed in successive individual sections. During the initial stage of the formation of the glass container a gob of molten glass is delivered to a blank station. The gob is then settled into the blank mold and a plunger is brought into active contact with the gob to cause it to form a parison having a shape peculiar to the type of glass container being manufactured.
The plunger is secured to a plunger head with a pair of split rings. In operation the plunger, the plunger head and the shaft upon which the plunger head is mounted reciprocate to bring the plunger in contact with the molten glass held in the blank mold. The plunger assembly is disposed in a cylinder to maintain axial control over the plunger, to accurately insert and guide the plunger into the blank mold, and to secure the split rings into a position which secures the plunger and the plunger head one to the other.
The plunger has internal passageways which transmit cooling air thereinto and therefrom. The pressure resulting from the air as well as other problems such as misalignment or misadjustment of the shaft which supports and directs the plunger causes the split rings to contact and strip away or abrade minute particles of metal from the encasing cylinder. Certain amounts of the metal particles inherently find their way into the glass parison to thus cause the glass to be contaminated.
The presence of these small particles of metal in the glassware greatly reduces the strength of the container and causes certain foodstuffs stored in the containers to undergo chemical reaction to thus contaminate the foodstuff. Accordingly, the pack rate of containers is adversely affected and the reject rate from users of the containers increases as the industry's cognizance of the imperfection increases.
Additionally, in order to cause the I.S. machine to produce a different type of container or to change the plunger in case of damage, it is necessary to stop the machine, remove the finish ring, rotate the plunger assembly to its extended position, remove the split rings, replace the plunger and repeat the procedure in reverse. Consequently, the replacement of a plunger causes a certain period of "down" time in which no ware may be produced and a resulting reduction in the efficiency of the machine.